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While various biomechanical factors should be considered to ensure favorable bone union between the fibular and mandibular bones following mandibular reconstruction using a fibula free flap, few studies have elucidated these factors. We performed biomechanical bone remodeling analysis at the bone union area of the reconstructed mandible using clinical follow-up computed tomography (CT) images of a patient who underwent mandibular reconstruction using a fibular free flap following mandibular resection and finite element analysis (FEA) based on the patientʼs CT data. This paper summarizes our newly-developed approach to estimating patient-specific masticatory muscle forces for performing highly accurate FEA; we also present a method for developing patient-specific bone remodeling algorithms based on computer-aided engineering simulation using clinical data and FEA results. In addition, this paper introduces various studies investigating the biomechanical factors that affect bone remodeling at the bone union site, such as the magnitude of occlusal force and optimal fixation conditions of the titanium plates, by using constructed patient-specific bone remodeling algorithms. [ABSTRACT FROM AUTHOR]

This paper describes a method for continuously measuring the contact position between the wheel and rail using strain gauges. The authors investigated the relationship between the bridge output sensitivity rate and the change in the placement of strain gauges using the result of finite element analysis for the instrumented wheelset. It is noted that the bridge output sensitivity rate is defined as the bridge output change per unit distance of the contact position (load position). Based on the result, strain gauges position suitable for measuring contact position was identified. On the other hand, static load tests were conducted on the instrumented wheelset with strain gauges attached to measure contact forces (wheel load, lateral force, and tangential force) and positions, respectively. The test results were found to be generally consistent with the finite element analysis results, and it was also observed that the load position of each contact force influenced each bridge output. Finally, this paper proposes a method for calculating the contact position by solving a nonlinear equation. The calculation uses the results of the load tests and also wheel rotation angle, bridge outputs, wheel load, lateral force and tangential force which measured in running railway vehicle. Simulations were performed for various cases, and the contact positions were obtained stably and continuously. This suggests that the proposed method is reasonable and applicable to various situations.

To evaluate stresses including stress concentration at weld toes for fatigue evaluation of complex shape welded structures such as railway bogie frames, previous studies proposed the stress assessment procedure through measuring strains of actual structures by attaching strain gauges with its edges to be at weld toes. This paper evaluates design fatigue strength in terms of the measured stress from published fatigue data and re-analysis of those fatigue tests. The obtained fatigue strength fell into danger side by 12-29% if compared to the fatigue strength estimated based on the current version of JIS. The result also showed that fatigue strength at 2×106 cycles with 0.13% failure probability had a similar value with that at 1×107 cycles with 2.3% failure probability. The fatigue strength in terms of the aforementioned strain measuring system was comparable with those in terms of structural hot-spot stress approach.

Tapping screw fabricates the female thread due to plastic deformation during screw rotation. Since the tapping screw skips the preliminary fabrication of female thread, it is widely used for the tightening in the fields of such as electric parts and car parts. However, there is a few theoretical studies for its self-tapping process and loosening proof. In this paper, we have investigated the mechanism of tapping torque and shape of female thread using three-dimensional finite element analysis. In addition to the plastic flow caused by the friction force due to the rotation of male thread, the plastic flow at the top of male thread separated by the up and down directions occurs. That contact at thread top mostly contributes the torque of self-tapping. Also, plastic flow along the lower surface of frank thread separated by the outside and inside radial directions creates the characteristic shape of female thread. The analysis results well reproduce the tapping torque and the shape of female thread. We also investigate the loosening proofs due to shear loading both for tapping screw and normal screw using there-dimensional finite element analysis. The shape of female screw obtained by self-tapping analysis is incorporated into the analysis model. It is found that the loosening proof of the tapping screw is superior to that of normal screw since contact at the top of thread in the lower part of tapping bolt inhibits the thread slip.

In this paper, the bending collapse behavior of sandwich U-shaped beam with lattice core has been investigated by using finite element analysis. In particular, the effects of geometric properties of lattice core and faceplate on the maximum bending moment Mmax and the critical angle θcr were discussed. The existence of lattice core could prevent the elastic buckling of the surrounding U-shaped beam, and enhance Mmax to the fully plastic moment of these plates. Based on numerical investigation, the mode map for θcr was obtained as a function of the relative thickness of the plate t/h and the relative density of the lattice core ρ/ρs.

The simultaneously iterative procedure proposed by the authors is extended to hyperelastic shells. The weak form of the equilibrium equation and the plane stress condition at every material point are defined as a coupled problem, and a numerical procedure based on the block Newton method to solve them with simultaneous linearization is developed in this paper. In the proposed block Newton method, the tangent moduli can be constructed algebraically by eliminating the internal variables, which are also updated algebraically without any local iterative calculations. In addition, the pseudo-stress for the residuals of plane stress state is incorporated into the linearized weak form of the equilibrium equation. Hence, the proposed procedure enables us to decrease the residuals in the coupled boundary value problems simultaneously. Some numerical examples demonstrate the validity and the effectiveness of the procedures in hyperelastic shells.

Recently, one of the authors proposed a multi-modal and multi-axis vibration reduction device against elastic vibrations of structures. The device is called eMDVA (embedded Mass Dynamic Vibration Absorber). The eMDVA consists of a ball-like mass embedded in a spherical viscoelastic material. Therefore the embedded mass can vibrate in every direction in the viscoelastic medium. The vibration characteristics of the eMDVA are investigated experimentally and numerically in this paper. Three eMDVAs with different sizes of spherical viscoelastic material containing a ball-like mass with a triaxial acceleration pickup are made, and vibration measurement tests are conducted. The measurement results show that the frequency response function (FRF) of the acceleration of the embedded mass versus excitation force has a single dominant peak. The peak frequency can be changed according to the size of the viscoelastic sphere. A finite element (FE) model of the eMDVA is developed, and investigations to determine the viscoelastic properties as Prony series expression are carried out. It has been shown that the ordinary procedure to adjust the Prony coefficients to fit the complex Young's modulus obtained by a dynamic mechanical analysis (DMA) leads to less accuracy in calculating FRF. On the other hand, good agreement between numerical and measurement results can be achieved by directly adjusting the coefficients to fit the FRF curves. In addition, FRF curves of the eMDVAs having non-spherical shaped viscoelastic material are calculated using the FE model with the viscoelastic properties mentioned above. The FE analyses have shown that by changing the shape of the viscoelastic material from sphere to spheroid or ellipsoid, the FRF has a different peak frequency according to the vibration direction.

In this paper, a three-dimensional finite element method based on damage mechanics has been newly applied to Turkey satin woven fabric composites, and the mechanical behaviors under damage development caused by on-axis tensile load have been investigated. From the on-axis tensile test and observation of damaged states for a Turkey satin woven fabric lamina, the computational results were proved to have good correlation with the experimental ones. Then, the effect of arrangement of weft yarns on damage development has been investigated numerically. As a result, the close arrangement of weft yarns increases the orientation angle of warp yarns, and accelerates occurrence and development of damages such as transverse cracks in weft yarns and shearing damage of warp yarns. Additionally, the maximum orientation angle of warp yarns was confirmed to be a dominant factor of damage behaviors, and to be kept under 5.26° for the Turkey satin woven fabric lamina. [ABSTRACT FROM AUTHOR]

Railway bogie frames are commonly constructed by welding several components. For a frame design, it is vital that all its welded joints have satisfactory strength and durability during their service life. This paper focuses on as-weld joints. The objectives include clarifying the influence of experimental stress assessment methods and developing analytical tools which are applicable to the design of as-weld joints in bogie frames. Static load tests were conducted on cruciform as-weld joints and machined test specimens using three different strain gauge attachment positions; finite element analyses (FEA) were performed. The results clarified that a new stress assessment method where the edge of strain gauge is attached at the weld toe shows the smallest deviation and little dependency on toe curvature radius variations. This suggests that the edge type strain gauge attachment is the best out of the three methods for stress assessment of as-weld joints. Moreover, the analytical stresses calculated from the FEA results agreed well with the experiments using the displacement differences corresponding to the strain gauge length. Appropriate FEA model shape and mesh size for the weld toes are proposed to calculate the edge type gauge stresses for the design of as-weld joints in bogie frames.

The prevention of excessive deformation by thermal ratcheting is important in the elevated temperature design of fast breeder reactors (FBR). In an experimental study that simulated a fast breeder reactor vessel near the coolant surface, it was reported that the long distance travel of temperature distribution causes a new type of thermal ratcheting, even in the absence of primary stress. Without excessive stress and travel distance, the inclement of the plastic strain derived from the above mechanism reduced each cycle of thermal transient, and finally reaches to approximately 0. In this paper, we investigate path independency on “saturated” distribution of plastic strain. For this purpose, we carried out several cases of finite element analyses with initial strain distribution, which simulated plastic strain distribution in the middle of accumulating. As the result, we confirmed that the shape of saturated distribution has small dependency on the shape of distribution in the middle of accumulating. Additionally, in the case using conservative initial strain distribution, further accumulation of plastic strain was not observed. This result suggests the possibility of the method that evaluate whether the accumulation of the plastic strain go beyond design limits.

It has been long since the technology for human space flight system was established. In order to realize challenging manned space missions, further improvements in the system reliability and crew safety are essential. Comprehensive design and operation considerations based on the quantitative crew safety analysis are key issues. Crew injury risk prediction method due to the transient dynamic load such as the excessive water landing speed, the explosion overpressure, and the off-nominal acceleration of the launch abort system (LAS) are developed and investigated in this study. In the early design stages, parametric injury risk analysis should be carried out. For this purpose, an anthropomorphic test device (ATD) model based on the multi-body dynamics is suitable to cover the wide range of conditions. In addition, an human finite element model is employed for more detailed crew injury risk analysis. Although there have been comprehensive research efforts in the automotive safety fields for many years, further research efforts are needed for the crew safety of human space flight since a wider range of the magnitude and the direction of the impact load should be considered. This paper deals with the human injuries evaluation using finite element model. The results are compared with those using Hybrid-III and safety margin is evaluated in view of NASA injury criteria to extract highly damaged body region in both models. The validity of brain injury criteria BrIC is investigated by using mechanical properties in brain and new risk curve for BrIC suitable for LAS environment is finally proposed.

A zirconium alloy cylindrical tube exhibited fracture under high-velocity axial impact load when high yield strength pellets were inserted as reported by Morishige et al., 2016. The fracture occurred after a crack was initiated at the tensile side of the bending tube. In this paper, FE analyses were conducted to clarify the fracture mechanism as well as the deformation behavior. At first, axial tensile tests using tubes with four slit-holes located at the center were performed in order to evaluate the fracture behavior of the tube. Then, digital image correlation (DIC) method was utilized to measure the local strain near the slit-holes. The results showed that the fracture displacement became smaller with smaller slit-holes’ radius. Also, the strain was concentrated at the slit-holes’ tips where cracks were generated before fracture. Subsequently, FE analyses of the tensile tests were conducted by LS-DYNA using the implicit method to obtain the fracture criterion. The load-displacement curve agreed well with the experiment. Then, the relationship between stress triaxiality and equivalent plastic strain near the slit-holes’ area were evaluated to define the fracture criterion. Finally, FE analyses of the axial impact tests using the dynamic explicit method were conducted to compare with the fracture criterion defined by the axial tensile tests. The results indicated that a localized stress and strain might occur at the tube boundary adjacent to pellets. This was caused by the interaction between tube and pellets’ edge which generated a tensile stress condition at the tube boundary when high yield strength pellet was applied. Under this condition, both stress triaxiality and effective plastic strain could increase and eventually lead to the fracture criterion.

This paper presents experimental, analytical and numerical study of impact perforation of steel plates with the aim to develop the procedures to assess the perforation of steel against tornado-generated missile impact. In the experiment, flat plates of SS400 steel and SUS304 stainless steel were perforated by a square pipe with cross section 200 x 300. Projectile mass and impact velocity were kept constant, namely, approximately 1300 kg and 17 m/s. Perforation limit thickness of SS400 and SUS304 flat plate was determined to be 9 mm and 6 mm, respectively. BRL formula was used for the analytical study, and equivalent diameter of square pipe for BRL formula was defined based on the experimental data. Numerical simulations of some experiments were also carried out and the effect of thermal softening and stress triaxiality on failure strain have to be taken into account in the material model in order to reproduce the experimental results.

With recent developments in the technology of intelligent materials, including shape memory alloys that deform autonomously depending on changes in the environment, such as temperature, it is expected that next-generation actuators that are simple, lightweight, and compact will also be developed. Consequently, in this paper, we investigated the disc spring type actuator made of Ti-Ni shape memory alloy (SMA), which is more compact than the conventional SMA coil spring type actuator. Firstly, prototype SMA disc springs were made from a thin SMA plate by metal stamping and shape-memory treatment. Secondly, we measured load-displacement curve of this prototype at both high and low temperatures. Thirdly, from the experimental results, the difference between displacements at low and high temperatures was used to estimate the performance (output displacement) of the SMA disc spring. The observations revealed that output displacement rate of the SMA disc spring was greater than 50% when the load was 30N. Compared to the coil spring, a similar effect would be obtained in approximately 37% of the space by the SMA disc spring. Finally, we conducted a finite element analysis of the SMA disc spring using a non-linear finite element analysis program, LS-DYNA. The validity of the analysis procedure was confirmed by comparing the analysis results with the experimental results.